Boat trailers are commonly used to transport boats such as outboard motor boats. These trailers have a tongue which connects to the vehicle by means of a ball and socket joint.
There are no wheels under the front tongue of the boat trailer so that when it is disconnected from the vehicle it is difficult to manoeuvre.
Conventional controls for providing a wheel support for the front tongue of the trailer generally comprises single wheel devices which are mounted on a long screw type jack arrangement. It requires a considerable amount of turning of the jack handle to retract the wheel sufficiently when the trailer is being transported by a vehicle.